The invention relates to a high-speed bearing assembly having particular application to the mounting of a textile spindle, wherein the inner raceways of two axially spaced antifriction bearings are circumferential groove formations on the spindle shaft itself.
In the past, belt-idler spindles and "friction-twister" spindles used in machines for the texturizing of synthetic-fiber filaments, as of nylon, rayon, polyester, etc. have been expected to run at speeds of 10,000 to 12,000 r.p.m., corresponding to a yarn speed of approximately 600 meters/minute, but recent competitive and other forces have dictated that yarn speed be doubled, meaning that spindles which had operated in the indicated range must now perform in the 20,000 to 25,000-r.p.m. range. The existing spindles have not been equal to the task and are the subject of frequent premature failure, thus necessitating shut-down for the awkward and uneconomic replacement procedure involved.
Typically, the spindle and bearing assembly which is subject to such failure comprises an elongate spindle shaft with two spaced raceways near one end. Outer race rings are assembled with a complement of balls at each of the inner raceways of the shaft, with a tubular spacer between outer rings to hold a fixed spacing of the resulting two ball bearings. The described components are assembled to the cylindrical bore of a mounting bushing, and ends of the bushing are inwardly deformed around axially outer limits of the thus-spaced outer rings, for permanent retention of the fixed spacing of the ball bearings. The outer contour of the mounting bushing is adapted for clamped mounting of the spindle and its bearing suspension on a mounting rail or the like of a textile machine.
It is my belief that failure of the indicated existing spindle-bearing assemblies at the indicated higher speeds is attributable to axial and/or radial looseness in one or both of the bearings. At high-speed rotation, each ball that is involved in such looseness seeks rotation about an axis of its own, and therefore pure-rolling contact of the ball with its raceways degrades, with accompanying skid-contact, meaning accelerated wear and tear. To replace a defective spindle-bearing assembly, the entire mounting bushing must be removed with the defective components which it contains.